Tamperproof bolt head having hidden tool engaging surfaces



Oct. 30, 1962 w. D. CORLETT EIAL 3,060,785

TAMPERPROOF BOLT HEAD HAVING HIDDEN TOOL ENGAGING SURFACES OriginalFiled June 50, 1959 E ark far/er United States Patent G 3,060,785TANIPERPROOF BOLT HEAD HAVING HIDDEN TOOL ENGAGING SURFACES Webster D.Coriett, River Forest, and Charles G. Mackie, Glen Eliyn, 111.,assignors to Standard Screw Company, Bellwood, 111., a corporation ofNew Jersey Original application June 30, 1959, Ser. No. 824,046, newPatent No. 3,034,386, dated May 15, 1962. Divided and this applicationJuly 11, 1960, Ser. No. 42,942

Claims. (Cl. 8S9) This invention relates to a fastener and in theparticular form here shown it is embodied in a tamperproof screw. Thescrew is designed so that it can only be removed by a particular tool,and hence cannot be removed by some unauthorized person. It is also, ofcourse, intended only to be inserted by the tool. The fastener as aWhole comprises a screw and an associated part, the purpose of theassociated part being to conceal the precise nature of the screw andalso to make the removal of the screw by some unauthorized toolimpossible, or substantially so. An object of the invention, therefore,is to make a screw or fastener so arranged that it can be inserted onlyby a special tool and removed by that tool.

Another object is to provide a screw or fastener so arranged that theprecise nature of the device is not ascertainable when it is inposition.

Another object is to provide a fastener which, whether used inconjunction with a special close fitting collar or in a confinedenclosure which provides in effect a collar, may not be removed byordinary tools such as a screwdriver, drift pin, punch, hammer, etc.,due to the inability of such tools to get a purchase on the fastener.

Other objects will appear from time to time during the course of thespecification and claims.

The invention is illustrated more or less diagrammatically in theaccompanying drawings wherein:

FIG. 1 is an exploded view showing the fastener, the protective andconcealing member and a part containing a threaded perforation or boreinto which the screw may be inserted;

FIG. 2 is a section showing the parts of FIG. 1 associated together ininterfitting and holding position;

FIG. 3 is a top plan view of the fastener or screw itself;

FIG. 4 is a bottom plan view of the screw; and

FIG. 5 is a fragmentary section with parts broken away showing the toolin position engaging the fastener, the fastener being in fully screwedhome position.

Like parts are indicated by like numerals throughout the specificationand drawings.

As shown in FIGS. 1 and 2, the fastener is associated with a fastenerreceiving member 1 which might be a bolt or a structural member or anypart of any shape so long as it is provided with a threaded perforationor bore 2. As shown the member 1 may be considered a plate or sheet orbar, or any other member in which it is desired to mount a tamperprooffastener. It may be of metal or wood. The invention is not limited toany particular material nor to a fastener which can be used in only aparticular material. Although the screw is shown more or less as amachine screw, it could be in the form of a drive screw or othercomparable fastener. In that case the thread would be quite differentfrom the one shown.

Although not necessary, it is convenient to have the threaded bore 2tapered or countersunk as at 3.

In the particular form shown the fastener includes the screw having athreaded shank 4 and an integral, laterally projecting portion 5 whichprovides, in efiect, a shoulder 6. This shoulder is preferably ofgreater diameter than the threaded portion 4. A head 7 is providedintegral with the shank 4 and the enlargement 6 and it is some-3,660,785 Patented Oct. 30, 1962 ice what wider than the enlargement 6.It projects outwardly beyond it as shown in FIGS. 1, 2 and 3. The top ofthe head presents a substantially uninterrupted surface when viewed fromabove and thus, for example, may be tapered as at 8 and flattened orrelatively flattened as at 9, taking thus the shape of a truncated cone.The head thus has what is sometimes referred to as a blind top. Theundersurface of the head is provided, as shown in plan in FIG. 4, with aplurality of radially directed outward extensions 10 which normallyextend flush with the outer edge of the head 7, as shown particularly inFIG. 4. In the particular form here shown there are three suchextensions 1% and they are spaced equally about the periphery of thehead of the screw. Between the extensions 16 there are depressions 11and these are suitable to receive the points of the tool, shown in partin FIG. 5. Such a tool is shown in full in our copending application,Serial No. 824,046, filed June 30, 1959, and now Patent No. 3,034,386.It will be noticed, particularly as shown in FIG. 4, that the portion ofthe head in which the extensions 10 and depressions 11 are formed issomewhat wider than the member 6 and thus there is provided a shoulderor ledge 12 about the member 6 and above it which is in reality thebottom of that portion of the head which contains the members 11 and 12.

in addition to the fastener proper or screw, there is included in thetotal fastener combination an enclosure. This is formed by the roundportion 13 which is open at its top as at 14 and is provided with a flatbottom 15 through which a perforation 16 is formed. The diameter of theperforation 16 is approximately that of the member 6 and when the partsare assembled together as shown in FIG. 2, all or a substantial portionof the portion 6 projects within the perforation 16 and lies against theupper surface 17 of the member 1 in which the fastener is received. Thethickness of the bottom 15 may be varied if desired, but preferably itwill be somewhat less than the height of the member 6 so that thefastener may be screwed tightly into position and will not be preventedfrom being so positioned by premature contact with the upper surface ofthe bottom 15.

The interfitting of the portion 6 and the perforation 16 results inholding the surrounding member 13 centrally with respect to the screw,and when the parts are assembled and the screw is fully engaged with thethread the parts will be centered fully as shown in FIG. 2 and thus anannular space of substantially equal width throughout its peripheryremains between the outer edge of the head 7 and the inner face of themember 13 so that the tool may be readily inserted within the member 13and engaged with the head in any position of relative rotation so thatthe prongs or points of the tool will fit into the depressions 11 andbeneath the edge of the head 7 and when turned will contact theextensions 10 so that rotation of the screw into and out of position maybe carried out. Once the screw is fully engaged, as shown in FIG. 2, itis completely surrounded by the member 13; the sides of the screw cannotbe examined and an unauthorized person cannot determine what the shapebeneath the head of the screw is for the purpose of attempting to use anunauthorized tool or some makeshift to remove the fastener. Thus, by theshape of the screw itself and its combination with the surroundingcuplike member a truly tamperproof fastener is produced.

As shown in FIG. 5 the parts of the fastener and the member 1 into whichthe fastener penetrates are the same as those shown in FIGS. 1 and 2,for example. A portion of a tool suitable for use in inserting andremoving the fastener also appears. The tool comprises a plurality ofjaw members or spring arms which are notched or grooved adjacent theirlower ends at 18 to provide a shoulder member 19. The lower face of eachspring member above the groove or notch 18 is beveled as at 26. As shownin FIG. 5, the shoulders 19 fit into the depressions 11 of the screw andmay engage the underface of the screw edge portion as shown. the screwand tool is prevented by the fact that the shoulder portions or ends 19of the spring arms as they lie within the depressions 11 are preventedfrom having any substantial relative rotation by the extensions orprojections 10. Thus the shape of the screw permits suitableinterfitting of the spring arms with the head of the screw so thatrotation of the tool, of which the spring arms form a part, causesrotation of the screw or fastener.

A plug member 22 is permanently positioned within the spring arms andthey are shaped to inter-fit. The cross-sectional shape of the plugmember is immaterial so long as it is shaped to cooperate with the innerfaces of the spring arms to prevent relative rotation of these parts.The plug supports the spring arms when they are in the position shown inFIG. and prevents distortion of them.

A member 25 is provided slidably along the fingers and along the tool ofwhich they form extensions. The tool is so shaped that when the member25 is raised away from the position of FIG. 5 the springs are free tomove outwardly and the tool may thus be disengaged from the screw.However, when the tool is engaged with the screw and it is desired tofasten the two together so that the screw may be rotated by the tool,the member 25 slides into the position shown in FIG. 5 and when it is inthis position the fingers are held with their shoulder portions 19 inthe position shown in FIG. 5, gripping the screw. The slidable sleeve 25is preferably flared outwardly to provide a skirtlike portion 27adjacent its lower end. The contour of the skirt portion 27 is providedinternally with a surface 28 to cooperate with the corre spondinglybeveled surface on the exterior of the spring arms or fingers. These twobeveled surfaces cooperate when the sleeve 25 is in the lowered positionof FIG. 5 to force the fingers inwardly into engagement with the screw.Only so much of the tool is shown and described as to indicate itsmethod of use, since the tool is fully shown and claimed in ourcopending application, Serial No. 824,046, filed June 30, 1959, of whichapplication the present application is a division.

Although an operative form of the device has been shown, the inventionis not limited to the particular details shown. Many changes may be madein the form,

shape and arrangement of parts without departing from the spirit of theinvention.

We claim:

1. A removable tamperproof fastener in combination with an enclosureencompassing the periphery and extending above the top of the fastener,said enclosure closely surrounding the outermost periphery of thefastener and being of a size suflicient to receive a fastener tool,

said fastener including a shank having means thereon for removablysecuring said fastener to a fastener receiving member by rotation,

Relative rotation of a peripherally uninterrupted head having agenerally circular side edge and a blind top,

the top surface of said head being relatively smooth and uninterruptedby projections or depressions, and

5 at least one projecting member extending circumferentially of the headand radially outwardly from the axis of the fastener,

said projecting member extending downwardly from the underside of saidhead, the lowermost periphery of said projecting member lying radiallyoutwardly from the axis of the fastener a greater distance than theradial extent of the shank,

said projecting member terminating in an abrupt shoulder facingdownwardly and disposed at a substantial radial distance outwardly fromthe axis of the shank,

the projecting member having surfaces so formed as to receive a tool,

said projecting member lying completely within the periphery of theradial extent of the head. 7

2. The removable tamperproof fastener of claim 1 further including astop member between the head and the shank, said stop member having adiameter less than the head and greater than the shank to thereby stopand space the head away from a fastener receiving member.

2 3. The removable tamperproof fastener of claim 2 further characterizedin that the stop member is formed integrally with the head and shank.

4. The removable tamperproof fastener of claim 2 further including aremovable protective and concealing member which limits visual andphysical access to that portion of the fastener beneath the exposed topthereof,

said protective and concealing member having a base wall with a agenerally centrally located aperture therein,the periphery of theaperture being larger n than the periphery of the stop and smaller thanthe periphery of the head,

said stop being slightly thicker than that portion of the base wallunderlying the head, and

a side wall extending generally upwardly from the base 40 wall adistance sufficient to substantially conceal the underside of the headfrom vision,

said side wall being spaced from the head a distance sufiicient topermit insertion of a tool engageable with the head.

5. The removable tamperproof fastener of claim 4 further characterizedinthat the thickness of the stop member is less than the thickness ofthe bottom wallof said concealing member.

References Cited in the file of this patent UNITED STATES PATENTS405,681 Rogers June 18, 1889 641,191 Champion Jan. 9, 1900 1,447,564Norlund et a1 Mar. 6, 1923 1,733,355 Morse Oct. 29, 1929 2,103,944Gullborg Dec. 28, 1937 2,133,465 Purtell Oct. 18, 1938

